The invention relates to a scanning electron beam device, particularly an electron beam tester or a scanning electron microscope, according to the preamble to claim 1.
A scanning electron microscope according to the generic concept of claim 1 is known for example from the document "Septieme Congres International de Microscopie Electronique, Grantable (1970)", pages 205 to 206.
In this the primary electron beam passes through a deflecting bridge which is formed by four magnetic prisms and by means of which the secondary electron beam is simultaneously deflected and separated from the primary electron beam to such an extent that it can be detected by a detector. A principal disadvantage of this construction is the multiple deflection of the primary electron beam which is necessary. It requires a high technical expenditure if on the one hand disturbing effects on the primary electron beam are to be avoided and on the other hand a great deflection of the secondary electron beam which is favourable for the installation of the detector is to be achieved.
A scanning electron microscope which is known from J. Vac. Sci. Technol. B 9(6), Nov/Dec 1991, pages 3010 to 3014 has similar disadvantages. In this case the deflection of the secondary electron beam emitted by the primary electron beam on the object is carried out by a Wien filter. However, without high technical expenditure and without negative expansions on the primary electron beam, only small angles of deflection can be achieved for the secondary electron beam with such an arrangement.
The object of the invention, therefore, is to construct a scanning electron beam device according to the preamble to claim 1 in such a way that the deflection of the secondary electron beam by a large angle can be achieved in a particularly simple manner.